Superpave Is Here to Stay, Despite Potholes on Some Roads

Mon March 15, 2004 - National Edition CEG

PITTSBURGH, PA (AP) Massive potholes on Interstates 279 and 81 to the contrary, state transportation officials said they haven’t given up on Superpave.

In fact, the asphalt-mixing technology that the U.S. Department of Transportation devised in a six-year, $50-million study is now used in all 50 states. And it has been a success in all but 15 of 800 road projects where it’s been used in Pennsylvania, said Gary Hoffman, Pennsylvania’s deputy secretary of highway administration.

Superpave isn’t a product but a technology in which pavement makers adjust the chemical formula of hot mix — which is comprised of crushed stone, sand and asphalt — depending upon a road’s climate and traffic density.

The potholes now plaguing I-279 near Pittsburgh — parts of which are known as the Parkway West — I-81 in Schuylkill County, and 13 other roads are simply the result of road crews and contractors learning how to use the technology, state transportation officials said.

“The parkway [I-279] was a very early application of Superpave and there was a learning curve involved,” said Rich Kirkpatrick, Pennsylvania Department of Transportation (PennDOT) press secretary. “Basically Superpave has reached the point where we expect it to be in use everywhere in the state and across the nation. That belies this idea that it’s [still] an experiment.”

PennDOT officials contacted The Associated Press two days after a regional PennDOT spokesman Dick Skrinjar, was quoted in the Pittsburgh media as saying the use of Superpave on I-279 was a “failed experiment.”

Federal highway officials said Superpave is no longer considered experimental, but is being used in approximately 65 percent of all federally-funded road projects. Generally, problems with Superpave result from other construction problems or from crews that are new to using the process, federal officials said.

“There’s no question that we have some major problems with the I-279 project. We will mill that off and repave it this year” using Superpave, Hoffman said.

Although Superpave costs up to 15 percent more than regular asphalt, it’s supposed to last up to 50 percent longer.

“On a typical, low-volume road, we can get 15 to 20 years of wear out of Superpave,” Hoffman said. “On a high-volume road with the old mix you’d get eight to 10 years.”

Superpave was developed between 1987 and 1993 by the federally funded Strategic Highway Research Program. University researchers in Alabama, Indiana, Nevada, Texas and Pennsylvania at the Northeast Center of Excellence for Pavement Technology at Penn State worked with the government to find solutions to rising road costs.

In warmer climates, asphalt can go soft and develop ruts. In colder areas, the asphalt can get brittle and crack. And in areas with temperature extremes, like Pennsylvania and most of the Midwest, it can do both.

By changing the polymers in the asphalt binder, as well as the percentage of stone and sand, different pavement textures can be created to suit different conditions.

On heavily traveled roads like Interstates 279 and 81, more crushed stone is used, which makes the road more durable, but also can make it more porous. Potholes are caused when water seeps through the pavement and freezes in pockets beneath it, causing the road to buckle when it thaws.

Hoffman said crews likely used too little asphalt binder on those roads, which were among the first in the state to use the new technology. More asphalt will likely be needed in the new mix to fix the problems.

On 98 percent of roads, the Superpave has performed well, particularly in preventing rutting, which occurs when heavy trucks wear tire-wide grooves in the road, which collect water and cause hydroplaning and other problems.

“We design the asphalt mix to withstand high truck loads. One 80,000-pound truck does the same amount of road damage as 10,000 car passes,” Hoffman said.

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